The present invention relates to a flat panel display device having a plurality of beam focusing guides for confining electrons in beams extending along channels in the device and selectively deflecting the beams toward a phosphor screen on the front wall at a plurality of points. Particularly, the present invention relates to such a display device in which the beams emitted from the guides impinge on the phosphor screen at substantially uniformly spaced points across the entire lateral dimension of the channels.
In my copending application for U.S. Letters Patent, Ser. No. 607,492, filed Aug. 25, 1975, entitled "Flat Electron Beam Addressed Device", now U.S. Pat. No. 4,031,427, issued June 21, 1977, there is described a flat panel display device which includes an evacuated envelope having parallel, substantially flat, rectangular front and back walls secured together in spaced relation by side walls. A plurality of spaced, parallel support walls extend between and are substantially perpendicular to the front and back walls. The support walls serve to provide internal support for the front and back walls against the external atmospheric pressure and divide the interior of the envelope into a plurality of parallel channels which extend along the front and back walls. At one end of each of the channels is a gun structure which is adapted to generate electrons and direct the electrons as beams into the channels along paths parallel to the front wall with each of the channels having therein at least one beam. Along each of the beam paths is a beam focusing guide through which the beam travels along the channel. The focusing guide serves to confine the electrons to the beam as the beam travels along the channel and to selectively deflect the beam toward a phosphor screen on the inner surface of the front wall at a plurality of points along the channel. At each point that the beams are deflected toward the phosphor screen the beams impinge on the screen to achieve a line scan of the screen.
It is desirable to minimize the number of support walls in the envelope so as to minimize the number of parts used to make up the display device and the weight of the display device. More importantly it is desirable to minimize the number of support walls so as to minimize the number of contact lines between the support walls and the front wall which can interfere with the visual display on the phosphor screen.
To minimize the number of the support walls, they are spaced apart a distance such that each channel contains a plurality of beams and therefore a plurality of beam focusing guides. The number of beams in each channel must be such that when the beams are deflected to impinge on the phosphor screen they will excite a line of the phosphor screen which extends laterally across the channel from one of the support walls to the other support wall. Also, the center to center spacing of the beams at their points of impingement should be uniform. However, it is desirable that the focusing guide which extends along the back wall of the envelope, be spaced from the support walls. This spacing is desired to prevent any possible interference with the operation of the focusing guides and to provide room for structure for mounting the focusing guides in the channel. Also, it is desirable that the path from the focusing guide to the phosphor screen of the electron beams closest to the support walls be spaced from the support walls to prevent the beams from charging the support walls. Thus, it would be desirable to have a display device in which although the focusing guides are spaced from the support walls the electron beams emitting from the focusing guides will impinge on the phosphor screen over the entire lateral dimension of the channel from one support wall to the other.